Learn about basic GUI components.

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Graphical User Interface (GUI) Components

• Learn about basic GUI components.
• Explore how the GUI components JFrame, JLabel,
  JTextField, and JButton work.
• Become familiar with the concept of event-driven
  programming.

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Graphical User Interface (GUI) Components

• Discover events and event handlers.
• Explore object-oriented design.
• Learn how to identify objects, classes, and
  members of a class.

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Graphical User Interface (GUI) Components

• View inputs and outputs simultaneously.
• One graphical window.
• Input values in any order.
• Change input values in window.
• Click buttons to get output.

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Java GUI Components
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Graphical User Interface (GUI) Components

• GUI components placed in content pane.
• GUI components
• Windows
• Labels
• Text areas
• Buttons

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GUI Components

• Added to content pane of window.
• Not added to window itself.
• Pixel A picture element.

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Windows

• Can be created using a Frame object.
• The class Frame provides various methods to
  control attributes of a window.
• Measured in pixels of height and width.
• Attributes associated with windows
• Title
• Width
• Height

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class JFrame

• GUI window instance created as instance of Frame.
• Provides various methods to control window
  attributes.

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Methods Provided by the class JFrame
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Methods Provided by the class JFrame
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Two Ways to Create a Window

• First way
• Declare object of type JFrame.
• Instantiate object.
• Use various methods to manipulate window.
• Second way
• Create class-containing application program by
  extending definition of class JFrame.
• Utilize mechanism of inheritance.

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Content Pane

• Inner area of GUI window (below title bar, inside
  border).
• To access content pane
• Declare reference variable of type Container.
• Use method getContentPane of class JFrame.

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Methods Provided by the class Container
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class JLabel

• Labels Objects of a particular class type.
• class JLabel Used to create labels.
• Label attributes
• Title
• Width
• Height
• To create a label
• Instantiate object of type JLabel.
• Modify attributes to control display of labels.

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Methods Provided by the class JLabel
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Methods Provided by the class JLabel
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class JTextField

• Text fields Objects belonging to class
  JTextField.
• To create a text field
• Declare reference variable of type JTextField.
• Instantiate object.

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Methods Provided by the class JTextField
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class JButton

• Provided to create buttons in Java.
• To create a button
• Use the same technique that is used to create
  JLabel and JTextField.

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Methods Provided by the class JButton
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Methods Provided by the class JButton
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Handling an Event

• Action event An event created when JButton is
  clicked.
• Event listener An object that receives a message
  when JButton is clicked.
• In Java, you must register the listener.

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Handling an Event

• class ActionListener
• Handles action event.
• Part of package java.awt.Event.
• The class ActionListener is a special type of
  class (interface).
• Must contain the actionPerformed method.

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Rectangle Program Sample Run
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Programming Example Temperature Conversion

• Input Temperature in Fahrenheit or Celsius.
• Output Temperature in Celsius if input is
  Fahrenheit temperature in Fahrenheit if input is
  Celsius.

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Programming Example Temperature Conversion

• Solution
• Create the appropriate JLabels, JTextFields,
  JButtons.
• Add them to the created content pane.
• Calculate the appropriate conversions when the
  buttons are clicked and an event is triggered.

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Sample Run for TempConversion
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Object-Oriented Design

• Simplified methodology
• Write down detailed description of problem.
• Identify all (relevant) nouns and verbs.
• From list of nouns, select objects.
• Identify data components of each object.
• From list of verbs, select operations.

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Summary

• Every GUI contains a window.
• Various components are added to the content pane
  of a window.
• class Frame is used to create windows.
• JLabel is used to label GUI components and
  display information to user.
• JTextFiled is used for input/output.
• JButton generates action event.
• Action event is sent to action listener.
• Action listener must have method called
  actionPerformed.